Because your domain record is public for all to see, some registrars want to upsell you to “privacy services” or “whois masking”, “private registration”, where they put their own info in the whois record instead of yours.
The important thing to know here is that in the eyes of the domain Registry to which all the Registrars interact, and the Registry’s oversight body (like ICANN, or in Canada, CIRA), whoever is listed in the domain whois record as the domain Registrant is the legal owner of the domain name. Keep that in mind, if you use a service like this, they own the domain, not you, notwithstanding whatever contract or Terms of Service you enter into with them to “own” this name on your behalf. If it lands in a dispute proceeding it will be an open and shut case: they own the name.
Taking it one step further, some “privacy” services will get you to sign up for the whois privacy service and then they turn around and happily offer to sell your true data to anybody else who cares to pay for it.